The invention relates to a method for operating a tire inflation system of a motor vehicle, said tire inflation system being composed of a compressed air source which contains a compression device and a pressure accumulator and from which inflation lines lead via inflation valves and in each case one control line per wheel leads via a control valve to a wheel valve, and of a control device. Inflation valves can be respectively assigned to a wheel or to an axle. Each wheel is assigned a control valve.
Tire inflation systems are currently used only in (usually armored) offroad vehicles for which the considerable structural outlay that they entail is not significant. However, in future they are also to be used in passenger cars, but here to increase driving comfort. In future it is to be expected that tire pressure monitoring systems will be legally required and then the additional expenditure will be smaller.
Austrian utility model AT 5548 U1 discloses a tire inflation system of the generic type in which the tire pressure is measured by pressure sensors installed in the wheels. The transmission of data from the rotating wheel to the vehicle is problematic. It either takes place (as in AT 5548 U1) by means of sliding contacts and lines to a control unit which is fixed to the vehicle, or more recently has been carried out via radio. Exposed sliding contacts and data lines to the wheels are clearly disadvantageous. Transmission via radio requires in each wheel not only the sensors but also a transmitter (if only of very short range) and a power source, or a transponder. The measured values are generally not transmitted from all the wheels at the same time but in turn. The transmitters and receivers in the wheel and vehicle and the necessity to differentiate or separate the signals of the wheels from one another requires complex electronics. Owing to the transit time of the signals, the measurement is not even precise.
A further problem of all tire inflation systems is the necessity to provide, between the wheel and the vehicle, two compressed air connections, one for the inflation line and one for the control line which activates the wheel valve located in the wheel, said compressed air connections being embodied as rotary input means. Rotary input means are subject to increased wear for as long as they are under pressure. For this reason, the inflation line and the control line must be depressurized after each inflation process has ended. At the start of the next inflation process, they have to be filled up again. This entails a loss of compressed air and therefore an energy loss, which should be as small as possible.
The object of the invention is therefore to propose a tire inflation system and a method for operating it which solves the aforesaid problems, in particular that of measuring pressure in the simplest possible way.